The following correction was printed in the Guardian's Corrections and clarifications column, Tuesday April 24 2007

In the article below, we were mistaken when we wrote about Ségolène Royal's plans to host a musical picnic by the river Seine in her Poitiers constituency; the river Seine does not flow through Poitiers, which is in central south-west France.

France's presidential campaign winds up today with the candidates of the traditional right and left, Nicolas Sarkozy and Ségolène Royal, taking a clear, but not impregnable, lead into Sunday's election, according to opinion polls.

Candidates were planning an improbable succession of events, including football matches and a picnic, in a last-ditch attempt to win the hearts and minds of an estimated 16 million undecided voters.

The large number of floating voters has made the first-round ballot impossible to predict, and observers remain cautious given the surprise sprung by the National Front leader, Jean-Marie le Pen, five years ago. But surveys close to the cut-off point for the electioneering and opinion polls have suggested that a bid by the third-placed centrist candidate, François Bayrou, to edge into the reckoning, might now be flagging.

Yesterday two polls from Ipsos and BVA suggested that between 29% and 30% of voters would support Mr Sarkozy, between 23.5% and 25% would vote for Ms Royal, between 15% and 18.5% for Mr Bayrou, and 13% for Mr Le Pen.

The two leading candidates will face a head-to-head second vote a fortnight later.Today the leading candidates will stage wildly differing campaign events, with Mr Sarkozy heading for the Camargue, in southern France, for a rendezvous with rice farmers, and Ms Royal hosting a musical picnic by the River Seine in her Poitiers constituency. Mr Bayrou is in Rouen for a rally.

Mr Le Pen is, according to his Paris headquarters, doing nothing. Controversial to the end, the far-right candidate had earlier told an Israeli newspaper that French Jews should vote for him. For good measure, he also tried to discredit his rightwing rival by dropping hints that Mr Sarkozy and his wife, Cécilia, were having new marital problems.

At the same time Mr Sarkozy's backers launched a "72 hours to win" campaign that includes a football tournament in the shadow of the Eiffel Tower. About 25,000 activists, armed with tracts, T-shirts, badges, balloons and bracelets, will work the country to persuade the electoral ditherers to vote for him.

Mr Sarkozy's election team is said to have been rattled by hints that his campaign posters were being destroyed more than those of other candidates - and worse, defaced with Hitler moustaches.

Concerns about the reliability of polling figures were heightened last night when a survey at the respected Paris Institute for Political Studies predicted a first-round victory for Ms Royal. The 1,000 students who took part in the mock vote gave her 39.8 %, Mr Bayrou 26.6 %, Mr Sarkozy 18.7 % and Mr Le Pen 4.8 %.

A college spokesman, Hervé Marro, denied that those at the university, a hothouse for many of France's future leaders, were traditionally leftwing. "Not at all. There are a lot of students at Sciences Po who normally support the right, which is why the result was such a surprise," he told the Guardian. "Additionally, a lot of the left-leaning students are not those who support Ségolène Royal."

He added: "The big problem with all polls is that saying you are going to vote for a candidate and actually doing so are two very different things."

Yesterday the newspaper Libération, pointing out that the election featured a dozen candidates, including a walrus-moustached anti-globalisation campaigner, a hunting, shooting, fishing defender, and three Trotskyists, asked: "What country in the world could align such a collection of political oddities? Clearly the most political country in the world is proving its inexhaustible electoral creativity."

Tonight at the stroke of midnight, under French election law all the candidates, along with the pollsters, will fall silent. Then, after weeks of sound and fury, the suspense will really begin.